#include <iostream>

int main() {
    int x,y;  //x为零食编号，y为零食数量
    float A=4.00;
    float B=4.50;
    float C=5.00;
    float D=2.00;
    float E=1.50;

    scanf("%d%d",&x,&y);
    switch (x) {
        case 1:
            printf("%.2f",y*A);break;
        case 2:
            printf("%.2f",y*B);break;
        case 3:
            printf("%.2f",y*C);break;
        case 4:
            printf("%.2f",y*D);break;
        case 5:
            printf("%.2f",y*E);break;
    }
    return 0;
}
